The present invention relates to the automatic production of filter paper bags containing infusion products such as tea, chamomile and similar herbs designed to be immersed in a liquid in order to make infusions.
In particular, the invention relates to an apparatus for preparing and feeding materials used to make the filter bags and is designed to be advantageously fitted to an automatic production machine.
In the automatic production of filter bags for infusion products, prior art teaches the use of filter paper bags with twin-pouch containment chamber, also known as xe2x80x9ctwo-lobed filter bagsxe2x80x9d, made by heat-sealing, that is to say, by suitably folding the filter paper and then sealing it along the folds by thermally activating a layer of glue spread on the web of filter paper during the original filter paper manufacturing process.
Bags made of heat-sealable filter paper are normally heavier than bags of the same size and shape in which the containment chambers which hold the charges of product are made by folding alone.
Since the cost of the paper is proportional to its weight, the greater weight of the bags made of heat-sealable filter paper means that, all other conditions being equal, they are more expensive than those made using folding alone. To make bags made of heat-sealable paper economically competitive with bags made by folding alone, it is common practice to give the bags made of heat-sealable paper smaller overall dimensions than those of the corresponding bags made of folded paper.
This leads to another problem, well known in the field of automatic machinery for making this type of product and that is, how, during the entire production process, to arrange and control the thread connecting the tag to the chambers that contain the infusion product.
In some types of filter bags, this problem has been solved by winding the length of thread around the containment chamber and securing it in this position. In such cases, however, the thread is precisely as long as the outline of the filter bag and, if the filter bag is made of heat-sealable paper, the smaller size of the filter bag means that the working length of the thread available is shorter.
Thus, if the infusion is prepared in certain types of tea-pots or in particularly tall cups or glasses, the thread length may be insufficient to prevent the tag from accidentally slipping over the edge of the infusion container during infusion and falling into the infusion liquid, with obvious consequences in terms of hygiene and/or pick-up tag recovery.
To overcome this drawback, patent document IT BO 2002A000013, in the name of the same Applicant as the present, proposes a filter bag and a method for making it, where the length of the thread is completely independent of the length of the outline of the filter bag containment chamber. More specifically, the thread is considerably longer than the outline of the filter bag.
The longer thread which, if left uncontrolled, would create serious problems for the automatic production process, is associated with a tagxe2x80x94in particular a twin-flap tagxe2x80x94and a portion of it is gathered and held between the flaps of the tag.
This solution, however, inevitably involves the need to provide suitable means especially adapted to implement a method for producing filter bags of this type on an industrial scale.
In this context, a highly critical role is that of preparing, reciprocally associating and feeding the materials used to make the filter bags prior to actually forming the containment chambers and placing the charges of infusion product in them.
The present invention has for an aim to solve the above mentioned problems through an apparatus that is capable of operating at high speeds; that is reliable; and that, at the same time, has a relatively simple and economical structure.
In accordance with the invention, these results are achieved by an apparatus for preparing and feeding materials used to make filter bags to contain an infusion product, the apparatus comprising the following arranged in succession around the edge of a power-driven revolving wheel:
first means for forming filter bag pick-up tags from a web of suitable material and arranging them in suitable order around the edge of the revolving wheel;
second means for feeding a continuous thread and forming in it first loops at regular intervals from each other at positions corresponding to the tags carried by the revolving wheel;
third means acting on the tags for delimiting separate faces on each tag and folding these faces onto each other in such a way that the first loops of thread are held between the tag faces;
fourth means for joining the faces of each tag to each other;
fifth means for associating a web of filter paper to the edge of the revolving wheel and positioning it above the continuous thread and the tags connected to it;
sixth means associated with the revolving wheel for pushing a portion of the continuous thread stretched on the edge of the wheel through the web of filter paper in such a way as to form a second loop extending outwards from the wheel and protruding from the face of the filter paper web opposite the face adjoining the tags.